The invention relates to an improved wear resistant assembly that may be used in machinery subject to wear due to abrasive contact, such as crushers, picks, grinding mills, roller cone bits, rotary fixed cutter bits, earth boring bits, percussion bits or impact bits, and drag bits. More particularly, the invention relates to wear resistant assemblies comprising superhard inserts. Such inserts typically comprise a super hard material layer or layers formed under high temperature and pressure conditions, usually in a press apparatus designed to create such conditions, cemented to a carbide substrate containing a metal binder or catalyst such as cobalt. The substrate is often softer than the super hard material to which it is bound. Some examples of super hard materials that high temperature high pressure (HPHT) presses may produce and sinter include cemented ceramics, diamond, polycrystalline diamond, and cubic boron nitride. An insert is normally fabricated by placing a cemented carbide substrate into a container or cartridge with a layer of diamond crystals or grains loaded into the cartridge adjacent one face of the substrate. A number of such cartridges are typically loaded into a reaction cell and placed in the high pressure high temperature press apparatus. The substrates and adjacent diamond crystal layers are then compressed under HPHT conditions which promotes a sintering of the diamond grains to form the polycrystalline diamond structure. As a result, the diamond grains become mutually bonded to form a diamond layer over the substrate face, which is also bonded to the substrate face.
Such inserts are positioned in regions of machinery that are subject to high levels of wear. The inserts then are often subjected to intense forces, torques, vibration, high temperatures and temperature differentials during operation Normally the region surrounding the insert is more susceptible to wear than the insert. As a result, insert stability may be compromised by erosion of the surrounding region long before the expected life of the insert is expired.
U.S. Pat. No. 5,848,657 by Flood et al, which is herein incorporated by reference for all that it contains, discloses domed polycrystalline diamond cutting element wherein a hemispherical diamond layer is bonded to a tungsten carbide substrate, commonly referred to as a tungsten carbide stud. Broadly, the inventive cutting element includes a metal carbide stud having a proximal end adapted to be placed into a drill bit and a distal end portion. A layer of cutting polycrystalline abrasive material disposed over said distal end portion such that an annulus of metal carbide adjacent and above said drill bit is not covered by said abrasive material layer.
U.S. Pat. No. 5,417,475 by Graham et al, which is herein incorporated by reference for all that it contains, discloses a breaking or excavating tool that has a diamond and/or cubic boron nitride coated cutting insert mounted at the forward end of a tool body which is made of a softer material than the inert. A separately formed retaining member such as a washer, ring or sleeve, made of harder material than the body, is brazed to a front face of the body surrounding the insert to protect the tool body against wear.
GB Patent No. 2,004,315 by Pietsch, which is herein incorporated by reference for all that it contains, discloses a rock cutting tool comprising a steel shaft having an end portion which tapers towards the end of the shaft and contains a hard metal pin, the said portion being surrounded by a ring of hard metal.